There exists a need in the art to provide a compact and self-contained lighting for a display hologram, which can produce high quality images and which is insensitive to stray light, particularly other near-point source lights (such as halogen spot lamps) or any other lighting sources used for ambient illumination near the direction of the main light source used to illuminate the hologram.
Although there have been previous ways of creating holograms all of these have particular difficulties. For example, U.S. Pat. No. 6,366,371 B1 which relates to use of a reflection hologram in transmission geometry has poor efficiency and stray light control. Furthermore, although GB 2 178 866 describes ways to fold light around to form a hologram there is no disclosure of transmission geometry and also has poor efficiency and stray light control. U.S. Pat. No. 6,366,371 B1 and GB 2 178 866 are incorporated herein by reference.
With the goal of making display holography a widely acceptable imaging media, e.g. for advertising or artistic displays, there are problems with conventional techniques which prevent widespread acceptance. Three of these problems specifically are:
(1) That typically the hologram and required illuminating light source are separate parts, requiring the light source to be installed separately from the hologram which is an extra complexity and is a barrier for users;
(2) The type of hologram which is most effective for displays (a reflection hologram) must be lit from the front, and is inherently sensitive to other ambient lighting, which in general causes unwanted ghost images; and
(3) Conventional broadband illumination from e.g. a tungsten lamp is inefficient and results in undesirably high image haze and consequently low image contrast. It is an object of at least one aspect of the present invention to obviate or mitigate at least one or more of the aforementioned problems.
It is a further object of at least one aspect of the present invention to provide apparatus and a method for providing compact and self-contained lighting for a display hologram, which can produce high quality images and which is substantially insensitive to stray light, particularly other near-point source lights (such as halogen spot lamps) used for ambient illumination near the direction of the main light source used to illuminate the hologram.
It is a yet further object of at least one aspect of the present invention to provide holographic displays as a general graphic medium, suitable for advertising, technical and medical visualisation, and consumer applications (e.g. posters, 3D photographs).